Yeah there's a lot of bad stuff happening in the CMake config. Further, this doesn't appear to be used by the government. At least not RKI.

What's the issue with that?

The CMakeLists.txt is very poor. Just use find_package(Threads REQUIRED) and do target_link_libraries(... Threads::Threads), and use target_compile_features or target properties to set the C++ version. Right now the CMakeLists.txt requires the user to set that, at which point you might be better off with a Makefile...